The present invention is directed to the field of semiconductor optical devices. More specifically, the present invention is directed to an optical connector and switching device for selectively directing an input optical signal into one or more optical output waveguides.
Bulk opto-mechanical switches are deployed in optical telecommunication systems to route signal traffic. U.S. Pat. No. 5,864,643 to Pan discloses a miniature 1xc3x97N opto-mechanical switch. Opto-mechanical switches require at least one of the input or output fibers to be physically translated among one of two positions. An array of mechanical switches are interconnected to form an optical cross-connect matrix switch. Bulk opto-mechanical switches are desirable for their low cost, low insertion loss, their insensitivity to polarization, and their very low levels of cross-talk. Mechanical switches suffer, however, from low speeds dictated by the mechanical movements of the switching components. The typical response time for such devices is on the order of about 0.001 to 10 seconds.
U.S. Pat. No. 5,774,604 to McDonald discloses a micro electro-mechanical 1xc3x97N switch in which an offset mirror is stepped into different positions to allow one of several fibers to be selected as the output port. The input optical signal may be re-directed by relatively small movements of the micro-mirror so that the response time of the switch is reduced as compared to bulk electromechanical switches. The physical movement required by each type of device, however, limits the switching response time to the hundreds of nanoseconds.
Micro electro-mechanical systems technology has recently been applied to the fabrication of optical switches. Researchers at the University of California at Los Angeles, IEEE Photonics Technology Letters Vol. 11, No. 11, November 1999, formed a vertical micro-mirror by self-assembly on a stress-induced curved polysilicon cantilever. Switching is accomplished by urging the mirror in and out of the path of two pairs of crossing optical fibers upon applying an electro-static electrical current between the cantilever and the substrate. Other integrated optic designs provide an imbedded waveguide which is connected and disconnected by the motion of a micro-bubble. For example, scientists at NTT opto-electronics laboratories, as reported in the Journal of Lightwave Technology, Vol. 17, No. 1, January 1999, have demonstrated a micro-electronic device in which the switching mechanism is based on the capillary effect induced by a temperature gradient.
Further, U.S. Pat. No. 5,889,898 to Koren et al. discloses a semiconductor integrated optical Y-branch switch. The two legs of the Y-branch switch each contain a serially-aligned first section where the local refractive index is controlled electrically as well as a second section where the optical loss is controlled electrically. For a signal to pass through a selected leg of the Y-branch switch, the selected leg is electrically controlled to have both a high refractive index and low absorption sections in series. Meanwhile the non-selected leg of the Y-branch switch is set to having both a low refractive index section in series with a high absorption section. As each leg or the switch requires two control signals to effect selection, four control signals must be directed to the switch in order to both propagate a signal and reduce cross-talk between the legs of the switch.
There is therefore a need in the art for an opto-electronic switch employing only a locally-controlled refractive index for selectively directing an input light signal among multiple output channels through a single steering section.
The present invention provides a semiconductor optical device that allows an optical connection to be made between one input port and one or more selected output ports. The input optical signal is launched into a single mode ridge waveguide that connects to a central beam-steering section. An array of ridge waveguides placed at the other end of the beam-steering section serves to collect the steered optical beam. An input optical signal is launched via a single-mode waveguide into the center region of a slab channel located between two contact strips through which electrical currents are injected. The presence of the charged electrical carriers forms anti-guiding regions of lower refractive index than the immediate surroundings. The region with the least amount of electrical carriers has the highest refractive index and the optical signal is confined to that region. By controlling the relative strengths of the current injections in the two contact strips, the region of highest refractive index can be selectively positioned back and forth between the contact strips. Consequently, the input beam is transported to one of the single-mode output waveguides. When the injected current densities are very low, the output optical beam spreads to all of the output waveguides and gives rise to a broadcasting scenario. Other intermediate currents are used to direct the optical signal to several output waveguides simultaneously hence performing the task of selective multi-casting.
The present invention provides an active semiconductor optical switch for a 1xc3x97N interconnect switch having an input light channel; first and second output light channels; and a steering section coupled between the input and output channels. The steering section selectively directs an input light signal from the input light channel to at least one of the first and second output light channels. The steering section may alternatively direct an input light signal to one or both of the first and second output light channels. The steering section includes transversely-spaced first and second elongate electrical contacts and an elongate slab waveguide extending therebetween. The slab waveguide is formed from a material having an optical refractive index responsive to a first electrical current applied to either of the first and second electrical contacts. Application of an electrical currents to the first and second electrical contacts varies the refractive index of the localized channel waveguide so as to steer the input light signal to at least one of the first and second output channels. The switch of the present invention may provide two, three, four, or more selectable output light channels.
Alternatively stated, the present invention provides an active semiconductor optical waveguide for a 1xc3x97N interconnect switch providing a single input channel and N output channels. The steering section of the switch is capable of directing light from the input channel to M output channels, where M is a number between one and N.
Switches formed according to the present invention are useful for creating a monolithic 1xc3x97N matrix switch having each output light channel of a first switch optically-coupled to an input light channel of another switch. Successive switches may be similarly cascaded to provide a single input channel having multiple selectable output channels.